Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to a device for the decontamination of surfaces, by means of a composite jet of compressed air, a fine sprayable particulate and a liquid, comprising a mixing chamber in the shape of a body of revolution supplied axially by said liquid and obliquely and eccentrically with respect to the axis of said chamber with the mixture of air and fine particulate, said chamber communicating with a spray nozzle.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98
The use of equipment for cleaning surfaces, in particular the facades of buildings or monuments contaminated by atmospheric pollution or the passage of time, or by deliberate action (graffiti), has been known for several years. Such equipment basically comprises the use of a jet of compressed air comprising a fine sprayable particulate usually known as abrasive and the use of a liquid which in most cases is clear water. One of the important elements of this equipment, besides of course the various machines supplying the air, water and fine particulate, is the nozzle itself mounted on a control handle. Such a control handle is described in FR B 2,753,643, the content of which is incorporated by reference, by the same inventor. The nozzle in that equipment has a very important function because its construction and geometry are such as to give the jet a movement of rotation about an axis, thus making it possible to reproduce to a greater or lesser degree a rubbing movement over the surface that is to be decontaminated. The nozzle is a component that suffers wear, if only because of the presence of the fine particulate and the pressure to which this particulate is subjected. In theory, the materials used exhibit high resistance to abrasion by said particulate. Nevertheless, after a certain number of uses said nozzle must be replaced if the efficiency of the jet is not to be diminished. At present, when the work is no longer done satisfactorily the nozzle is replaced, instead of replacing only the part which is worn. This part is often the upstream part of the mixing chamber which is the first to receive the jet of air and the fine particulate.
U.S. Pat. No. 4,648,215, the content of which is incorporated by reference, provides a production method based essentially on the presence of a high-pressure liquid which entrains the abrasive and the air (by the Venturi effect) to form a jet, an apparatus and a nozzle for carrying out the method.
Document DE-A-40 02 787, the content of which is incorporated by reference, provides a nozzle, the entrainment of the abrasive being provided by a liquid.
The present invention is directed toward a nozzle in which the abrasive is displaced by compressed air, the liquid having more a function of comfort, namely to ensure that the dust produced in the course of decontamination does not either inconvenience the user or pollute the surrounding air. In certain situations, the water supply can be turned off without reducing the desired effect.
It is an object of the present invention to provide a novel nozzle that overcomes the abovementioned drawbacks.
The decontamination device according to the present invention consists of an outer body with a cylindrical bore housing the mixing chamber, a sleeve of approximately cylindrical shape with means for fitting it to said outer body and housing in a bore a second body of revolution forming said spray nozzle; while said outer body is provided with a first inlet for the supply of liquid in the axial direction to the mixing chamber, and with a second inlet whose axis is oblique and offset from that of the mixing chamber for the entry of the mixture of air and fine particulate; and said second inlet is situated in such a way that the mixture of air and fine particulate reaches the inner wall of the mixing chamber near its upstream end and is offset from the axis of the mixing chamber toward the left when on the northern hemisphere and toward the right when on the southern hemisphere so that the jet of air and sprayable material benefits from the Coriolis effect.
The advantages of the nozzle according to the invention are the fact that it consists of four main components, namely the outer body which takes the mixing chamber, and the sleeve which protects the nozzle itself and is also a body of revolution. These are individually interchangeable, so only the worn part or a part that has become damaged need be replaced, rather than replacing the whole of the device as in the current practice. In addition, the fact that the jet of air and fine sprayable particulate falls onto the end of the chamber means that the entire length of the chamber can be used to give it the desired movement in order to obtain maximum efficiency of the nozzle outlet, unlike what happens in devices that use the liquid as a vehicle for the particles. Also, the fact that the second inlet is offset from the axis of the mixing chamber so that the jet of air and sprayable material benefits from the acceleration due to the Coriolis effect makes it possible to obtain maximum kinetic energy at the nozzle outlet and therefore great efficiency. This displacement must of course take place either to the left or to the right, depending on which hemisphere of the earth of the device is being used.
Another advantage also is the fact that the mixing chamber can be reused if it is rotated for example through 180xc2x0, thereby doubling the life of the mixing chamber, which is a substantial economy. It would also be possible to regulate the life of the chamber if the chamber is rotated through 120xc2x0, which offers an even more substantial economy. Thus, for the component which suffers the greatest wear, it is possible either to extend its life by rotating it through 180xc2x0 or 120xc2x0 inside the outer body, or to replace it well before replacing the nozzle which suffers less wear and in any case symmetrical wear because in this part the jet is moving helically, but always in the tangential direction relative to the wall of the nozzle, which is not true of the jet when it first strikes the upstream part of the wall of the mixing chamber.
In an alternative embodiment, the mixing chamber is formed by a cylindrical upstream part and a narrowing conical downstream part thus allowing the jet to pass through the interior of the mixing chamber toward a cross section of decreasing diameter in order to reach the next component which is the nozzle itself.
In another alternative embodiment, the inlet for the supply of air and particulate comprises a rod made of an abrasion-resistant material which is screwed into a tapped hole in the outer body and is surrounded by a bushing, made preferably of plastic, and the pipe for the supply of air and fine particulate is attached to this bushing by a screw thread or other means.
This construction also provides an inlet which has good resistance to the abrasion caused by the fine particulate. This rod can therefore be replaced when worn without having to replace the entire inlet device and this also makes for a component whose cost is not very high, which would be the case if this inlet were made from a single piece of abrasion-resistant material.
In another alternative embodiment, the mixing chamber also ends on its outer part in a cone which becomes narrower and mates with the second body of revolution whose upstream end is a complementary surface so that it is possible by connection to form a continuous channel between the mixing chamber and the outlet nozzle.
In another alternative embodiment, the wall of the mixing chamber comprises upstream a conical part that narrows toward the center of the chamber, followed by a cylindrical part, followed by a narrowing conical part, and the downstream end of said mixing chamber has an annular surface by which it bears against a corresponding annular surface of the second body of revolution.